The invention belongs to the technical field of fermentation and discloses a method for extracting glutamine from fermentation liquor. The method comprises the following steps of: cooling and filtering glutamine fermentation liquor, concentrating, cooling and crystallizing the obtained filtrate, and separating to obtain a crystallized crude product; adding 30-60 weight percent of water for washing the crystal, and separating to obtain a crude product in which the crystal is washed; and adding water for dissolving, sequentially adding a cation exchange resin and an anion exchange resin for removing salt, and filtering to obtain desalted liquid; performing nanofiltration to obtain nanofiltration liquid, decolorizing and filtering to obtain decolorized solution, concentrating, cooling, crystallizing, separating and drying to obtain glutamine. According to the method, the crude product is washed and crystallized, most of impurities on the surface of the crystallized crude product are removed, and the amount of the desalted resin is reduced, so that the sewage quantity is reduced, the energy consumption is reduced, and the pollution is reduced; and meanwhile, the method of sequentially adding the cation exchange resin and the anion exchange resin into the feed liquid is used for desalting, the glutamine loss caused by long desalting period is greatly reduced, and the yield of the glutamine is improved.